Honeywell Q674L User Manual

T874R Thermostats and Q674L Subbases

Installation Instructions for the Trained Service Technician.

INSTALLATION INSTRUCTIONS

APPLICATION

The T874R Thermostat and Q674L Subbase provide 24 to 30 Vac control of 2-stage heating and 1-stage cool-ing heat pump systems with manual changeover. Q674L Subbase provides EM.HT.-HEAT-OFF-COOL system switching and AUTO-ON fan switching. See Table 1 for specific T874R/Q674L combinations.

Table 1. Thermostat/Subbase Specifications.

Thermostat/

Subbase

Model

Numbers

Q674L1207

Q674L1520

Q674L1587

Q674L1710

Q674L1736

T874R1905/

Q674L1777

T874R1913/

Q674L1777

Q674L1827

Q674L1868

LED

Indication Changeover Comments

AUX.HT.,

EM. HT.

AUX.HT., EM. HT.

AUX.HT.,

EM. HT.,

CHECK

AUX.HT.,

EM. HT.,

CHECK

EM. HT. Manual Cool

AUX.HT., EM. HT.

AUX.HT.,

EM.HT.

Manual Cool

Manual Heat

or Cool

Manual Heat

or Cool

Manual Heat

or Cool

Manual Cool Requires C815A Outdoor Thermister

Manual Heat

or Cool

TRADELINE®; adjustable stage 2 heat anticipation. Fixed anticipation in stage 1. Auto fan in EM.HT.

TRADELINE®; fixed heat anticipation. Auto fan in EM.HT.

SUPER TRADELINE®; fixed heat anticipation. Factory installed jumper across W1 and Y1. Auto fan in EM.HT.

TRADELINE®; fixed heat anticipation. Auto fan in EM.HT.

TRADELINE®; exact replacement for York model no. 2TH11702224.

TRADELINE®; exact replacement for York model nos. 2TH11702324 and 6TH11702224.

TRADELINE®; exact replacement for York model nos. 2TH11702324 and 6TH11702224. Includes C815A1054 Outdoor Thermistor.

TRADELINE®; exact replacement for York model no. 2TH11702224.

for outdoor reset. Fixed stage 1 heat anticipation. No heat anticipation in stage 2 heat. Auto fan in EM.HT. Replaces Y594R1136.

TRADELINE

See Fig.

Thermostat/

Subbase

Package

Y594R1243 T874R1152/

Y594R1300 T874R1475/

Y594R1425 T874R1616/

Y594R1615 T874R1822/

Y594R1664 T874R1871/

Y594R1672 T874R1889/

Y594R1698

Y594R1706

Y594R1763 T874R1954/

Y594R1797 T874R1988/

EM.HT. LED also shows compressor malfunction.

Premier White® color.

X-XX UL

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T874R THERMOSTATS AND Q674L SUBBASES

OPERATION

On a 2-heat thermostat, the two stages of heat sequentially as the temperature drops. mercury switch initiating a call for heat or cool.

There is about 1° F (0.6° C) between stages so the second stage makes only when the first stage can not handle the load. The 1° F (0.6° C) is referred to as the

differential

The light emitting diodes (LED) on the subbase light when something specific happens within the system. When an LED lights, refer to this list for the meaning:

NOTE: LEDs are not field replaceable or addable.

EM. HT.: Emergency heat is operating. The compres-

sor has failed, and the heat pump is not operating. LED lights when system switch is placed in the EM.HT. position by the homeowner.

AUX.HT.: Auxiliary heat is operating, which means the

weather is so cold that the heat pump cannot handle the load.

CHECK: System needs to be checked. See heating

sys-tem instructions for specific meaning.

RECYCLING NOTICE

This control contains mercury in a sealed tube. Do n place control in the trash at the end of its useful life.

If this control is replacing a control that contains mer-cury in a sealed tube, do control in the trash.

Contact your local waste management authority for instructions regarding recycling and the proper disposal of this control, or of an old control containing mercury in a sealed tube.

Make

refers to the

not

place your old

make

interstage

INSTALLATION

When Installing this Product…

1. Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.

2. Check the ratings given in the instructions and on the product to make sure the product is suitable for your application.

3. Installer must be a trained, experienced service technician.

4. After installation is complete, check out product operation as provided in these instructions.

CAUTION

1. Disconnect power supply to prevent electrical shock or equipment damage.

2. To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires as close as possible to the subbase.

3. Push excess wire back into the hole and plug hole to prevent drafts from affecting thermostat operation.

4. Do not overtighten thermostat captive mounting screws because damage to subbase threads can result.

5. Do not short across coil terminals on heating relay or gas valve. This can burn out the thermostat heat anticipator.

6. Never install more than one wire per terminal unless factory-supplied jumper with spade terminals is used.

IMPORTANT

Thermostats are calibrated at the factory using subbase mounted at true level. Inaccurate subbase leveling causes the actual temperature to deviate from the setpoint temperature.

Location

Install the thermostat about 5 ft (1.5m) above the floor in an area with good air circulation at average temperature. Do not install the thermostat where it can be affected by:

— drafts or dead spots behind doors and in corners. — hot or cold air from ducts. — radiant heat from sun or appliances. — concealed pipes and chimneys. — unheated (uncooled) areas such as an outside wall

behind the thermostat.

Mounting The Subbase

The thermostat subbase can be mounted on a vertical outlet box, horizontal outlet box or directly on the wall.

1. If you must mount the subbase on a vertical outlet box, order Honeywell 193121A Adapter Assembly. See Fig. 1. The assembly includes an adapter ring, two screws and a cover plate to cover marks on the wall. Install the ring and cover plate on the vertical outlet box.

For a wall installation, hold subbase in position and mark holes for anchors. See Fig. 2. Obtain wall anchors locally. Be careful that the wires do not fall back into the wall opening. Set aside subbase. Drill two 3/16 in. (5 mm) holes and gently tap anchors into the holes until flush with the wall.

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T874R THERMOSTATS AND Q674L SUBBASES

VERTICAL OUTLET

BOX

ADAPTER RING

MOUNTING SCREWS (2)

SUBBASE

HORIZONTAL OUTLET

BOX

NOT INCLUDED WITH UNIT.

ACCESSORY PARTS AVAILABLE (193121A).

SUBBASE

COVER PLATE

MOUNTING SCREWS (2)

Fig. 1. Installation of subbase on outlet box.

WALL

WIRES THROUGH WALL OPENING

M925

4. Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws.

5. Level the subbase by using a spirit level. Firmly tighten subbase mounting screws. See Fig. 3. The subbase mounting holes provide for minor out-oflevel adjustments.

IMPORTANT

An incorrectly leveled subbase causes the temperature control to deviate from setpoint.

Wiring the Subbase

All wiring must comply with local electrical codes and ordinances. Follow equipment manufacturer wiring instructions when available. To wire subbase, proceed as follows:

1. Connect the system wires to the subbase. See Fig. 5-12. A letter code for identification is located near each terminal. The terminal barrier permits straight or conventional wraparound wiring connection. See Fig. 4.

2. Firmly tighten each terminal screw.

3. Fit wires as close as possible to the subbase. Push excess wire back into the hole.

4. Plug the hole with nonflammable insulation to prevent drafts from affecting the thermostat.

SPIRIT LEVEL

TOP MOUNTING HOLES (2)

WIRING TERMINAL

THERMOSTAT CABLE OPENING

WALL ANCHORS (2)

M926

SUBBASE

MOUNTING HOLES

MOUNTING SCREWS (2)

Fig. 2. Installation of subbase on wall.

2. Run wires to the thermostat location.

3. Pull wires through the cover plate (if used) and subbase cable opening. See Fig. 3.

IMPORTANT

Use 18 gauge, color-coded thermostat cable for proper wiring.

MOUNTING HOLES (2)

POST (2) FOR MOUNTING THERMOSTAT

TO SPRING FINGER CONTACTS ON THE THERMOSTAT (UP TO 12)

Fig. 3. Subbase components and leveling procedure.

FOR STRAIGHT INSERTION– STRIP 5/16 IN. (8 MM)

SUBBASE TERMINAL SCREW

BARRIER

FOR WRAPAROUND– STRIP 7/16 IN. (11 MM)

Fig. 4. Wiring connections.

M927

M928

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T874R THERMOSTATS AND Q674L SUBBASES

THERMOSTAT

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

FIELD REMOVABLE JUMPER.

Fig. 5. Internal schematic and typical wiring diagram for Y594R1763 (T874R1954/Q674L1827). Replaces

FALL

GE AY28X078, AY28X139; Trane Baystat 139, Baystat 239 and Baystat 240;

THERMOSTAT

H1/C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.

and Honeywell Y594R1136 Thermostats.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

SUBBASE SYSTEM COMPONENTS

AUTO

FAN SWITCH

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

COMPRESSOR MONITOR

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

OUTDOOR THERMOSTAT

COMPRESSOR RELAY

SUBBASE

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

SYSTEM COMPONENTS

RTD 1 EHR 1

SYSTEM MONITOR

COOL CHANGEOVER VALVE

LACO

ODT 1

ODT 2

EHR 2 RTD 3

COMPRESSOR CONTACTOR

FAN RELAY

(HOT) L1

AUX. HEATER RELAY

OUTDOOR THERMISTOR

COOL CHANGEOVER VALVE

M2970

RTD 2

RTD 1

FAN RELAY

EM. HT. RELAY

CHP

M5072A

Fig. 6. Internal schematic and typical wiring diagram for Y594R1243 (T874R1152/Q674L1207).

L1 (HOT)

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